Function repository_jray_actors_at 

pub async fn repository_jray_actors_at(
    manager: State<'_, RepositoryManagerWrapper>,
    handle: String,
    item_id: String,
    t: f64,
) -> Result<Vec<JRayActor>, String>

Query the optional JRay plugin for the actors on screen at time t (seconds) in an item. Returns an empty list when JRay isn’t installed or has no data for the item, so the caller can render nothing without error.